1. Field of the Invention
The present invention relates to a safety syringe with attached needle.
2. Description of the Prior Art
Used needles and syringes, especially extended needles, pose a risk of transmitting infectious diseases from accidental needle sticks. Contaminated needles and syringes can carry blood-borne infectious agents, such as gonorrhea and syphilis bacteria, as well as hepatitis and HIV viruses. While medical personnel and sanitation workers are at risk, the general population is also at risk from improper disposal of the used needle and syringe.
Prior art safety syringes with retractable needles have many problems. These problems relate to complexity, reliability, repeatability, cost and ease of use. Because syringes are mass produced at the rate of millions per day, cost is a significant factor in manufacture of the parts and the assembly of the device. Automated production of parts and assembly of parts is critical in order to have any hope of supplying a practical syringe to the market.
A major drawback of prior art single use syringes is that single use syringes cannot be used to clear air bubbles from the medicine, to inject fluid to mix medicine within a vial or to rinse the needle and syringe with a different medicine before filling with the desired medicine. In many of these devices once the plunger is plunger all the way forward, the plunger locks the needle and retracts the needle within the barrel to prevent a second use.
A need exists for a multiple use retractable syringe for health care and other workers. Health care workers typically push the plunger all the way forward before withdrawing fluid from a medicine vial. The worker then partially withdraws fluid from a vial into the syringe. The worker next flicks the syringe to free trapped air bubbles before plunging the air and at least some of the fluid back into the vial. This step clears air trapped within the barrel. After clearing out the air, the user withdraws the fluid for use.
Health care workers often first inject fluid into a vial of medicine in order to mix the medicine with the fluid. After mixing, the worker withdraws the mixed medicine from the vial for injection. Likewise, health care workers may first rinse the needle and vial with another medicine before inserting the needle into a medicine vial and withdrawing the medicine. After use, the worker can retract the needle into the syringe to prevent any risk of harm from the needle to others.
In a curious development, healthcare workers in the drug control field have expressed a need for a reusable retractable syringe to prevent the spread of blood borne diseases, such as AIDS and hepatitis. Such a syringe is preferably a full displacement syringe which will deliver essentially all of the contents without retracting and without limiting the ability of the user to draw a second dose. Hopefully the drug user will confine use to himself without sharing the needle but can retract the needle when finished and render the device inoperable.
The present invention is designed to accomplish these goals and more.